Plasma sprayed and laser engraved field electron emitters

Plasma sprayed Cr2O3 coatings were engraved with the use of a CO2 c.w. laser in an installation for production of anilox rolls. The engraved cells had a ‘honeycomb’ geometry with different line densities and depths: 140 lines/cm with 35-μm depth, 180 lines/cm and 200 lines/cm, both 10 μm deep. The engraved surfaces were subsequently PVD coated with a Ti thin film. The microstructure of the coatings was characterized using scanning electron microscopy and optical microscopy. Finally, the measurements of the field emission current were carried out. It was found out that the greatest current was emitted from the surface engraved with the 34-μm deep cells. The emissions spots were presumably small, micrometer sized crystals generated at the solidification of laser molten Cr2O3.